The present invention relates to well downhole tools having tubing with a fluid bore and packers which isolate a zone of a cased or uncased wellbore and for controlling communication between the isolated zone and the tubing.
It is known to use a tool which straddles and isolates a zone in a well. One such tool is that described in U.S. Pat. No. 5,782,306 to Serafin. The tool utilizes inflatable packers spaced on a length of tubing, the packers being inflatable through a valve which shuts when the packers fully engage the well wall, and which then opens a fluid path between the tubing""s bore and the now isolated zone. There are challenges in applying such known technology to horizontal wells including that the downhole end of the tubing string becomes relatively insensitive to tubing manipulation and only gross movements are effective. There are also reliability issues when applying remote actuation systems such as umbilicals or darts for instructing a downhole tool. It has been generally found that there are several challenges yet to be overcome in running in, setting and operating these prior art forms of tools in a variety of onerous wellbore conditions, including:
use in horizontal wells which requires operations at remote locations and which are relatively insensitive to many conventional modes of tool operation including uphole/downhole movement, rotation, and tubing setdown weight;
where running in results in a higher pressure leading the tool than that trailing the tool;
where running in results in increasing differential pressures across various sealed components of the tool; and
where there is often a desire to set, release, move and reset the tool so as to stimulate or produce from other areas of the wellbore as conditions change.
There is also a desire for a tool which is able to handle the above challenges while being reliable in its setting; in other words, it is not inadvertently actuated during the run in, or on the trip out. Further, with the difficulties imposed by a typical horizontal open hole wellbore, it is also desirable to avoid use of unreliable tubing manipulation and mechanical means such as umbilical connections.
The tool of the present invention utilizes tubing to annular pressure differential to effect actuation of at least two spaced packers for straddling or isolating a zone in a wellbore. For open hole wellbore, the packers are large radially movement capable, such as segmented squeezable or inflatable packers. Uphole and downhole packers are positioned and spaced apart on a cylindrical spool or housing extending concentrically along a length of mandrel. The length of tubing between the packers determines the interval or length of zone which is affected. A wellbore annulus is formed between the housing and the open hole. A tool annulus is formed between the housing and the tubing. Within the tool annulus are formed a variety of annular shoulders, pistons and other devices which enable unique capabilities and operations. The tool can be used to enable a variety of zone isolated operations including: production out of the zone, stimulation into the zone, and swabbing operations.
The tool is operable without the need for precise tubing manipulation. Tubing manipulation positions the tool by running in and pulling out. In combination with varying the tubing pressures and gross manipulation of lifting and lowering the tubing, pressure differentials during running in and tripping out can be equalized, packers can be set and released, operations in specific zones or intervals can be performed and the tool can be relocated in the wellbore.
As the present tool does not need tubing rotation for actuation or operation, the tool is particularly well suited for coiled tubing operation where tubing rotation is not possible. Further, in horizontal wells where set down weight cannot be reliably gauged, the present tool is still operable. Further, the mechanisms in the tool annulus enable use of the entire diameter of the tubing bore for fluid flow, avoiding placing restrictive constraints on the tubing bore.
In another aspect, the tubing, housing and tool annulus are implemented in combination with a novel arrangement of annular retaining pistons, shoulders and a mechanical movement limiting stop, preferably a collet and spring-biased pressure actuated sleeve. The stop and annular retaining pistons enable various operations including subsequent operations pressure fluctuations or reversals without releasing the tool. Through application of a threshold pressure, a sleeve shifts and removes collet support. The collet is permitted to flex or collapse and thereby remove the stop. Release of the stop allows the mandrel to move further downhole in the housing for aligning ports therebetween and opening fluid flow to the zone between set packers. Movement of the mandrel uphole relative to the housing allows release of the packers and resetting of the collet stop in preparation for tripping out of the wellbore, or repositioning the tool. The stop and the tool can be reset using a gross axial movement of the tubing and mandrel.
In one broad aspect, a method is provided for establishing fluid communication with an isolated zone of a wellbore comprising: providing a tool having a mandrel and a housing, the mandrel having a bore and being adapted at an uphole end for connection to a tubing string and being closed at a downhole end, and the housing carrying an uphole packer spaced axially along the housing from a downhole packer, the housing being movable axially on the mandrel; positioning the housing on the mandrel at a first position for establishing fluid flow from the wellbore below the downhole packer, through the bore of the mandrel and to the wellbore above the uphole packer for running in the tool; positioning the housing on the mandrel position at a second position for blocking fluid flow between the bore of the mandrel and the wellbore above and below the packers and applying a first pressure in the bore of the mandrel to actuate the uphole and downhole packers and isolate the zone therebetween; and positioning the housing at a third position for maintaining actuation of the packers, for continuing to block fluid flow between the wellbore above and below the packers and for establishing fluid flow between the bore of the mandrel and the isolated zone. In another embodiment, at the third position, the method further comprising: misaligning outer bypass ports in the housing and inner bypass ports in the mandrel for continuing to block fluid flow between the wellbore above and below the packers; and aligning outer operation ports in the housing and inner operation ports in the mandrel for establishing fluid flow between the bore of the mandrel and the isolated zone.